The present invention relates to the field of dismantling structures, in particular dismantling containment buildings of a nuclear power station.
Traditionally, containment buildings of nuclear power stations are constituted by masses of reinforced concrete that are of considerable thickness. Certain masses may present lengths of concrete for drilling lying in the range 0.5 meters (m) to 30 m.
The term mass of “reinforced concrete” is used herein to designate a structure made of any kind of reinforced concrete, including metallic aggregate concrete, barytes concrete, or indeed prestressed concrete.
A specific feature of reinforced concrete is that it contains numerous reinforcing components, usually made of metal, such as prestress cables, steel bars, or any other metal reinforcement. Reinforced concrete thus presents high density. It is also very strong, presenting a breaking stress of the order of 40 megapascals (MPa) or more.
Operations of dismantling or destructuring a nuclear installation, including dismantling containment buildings of the installation, are thus generally lengthy and complex to undertake since they involve, cutting up reinforced concrete masses that are not only very thick but also very strong.
Among existing technologies, such as that described in DE 195 06 722, the use of diamond coring is known: a drill tube having a distal end fitted with an open cutter member is set into rotation in order to take a core out from the mass. After cores have beer, extracted, the portions of the mass situated between, the boreholes are cut up, e.g. by diamond wire sawing.
Such a method presents several drawbacks. In particular, it presents low efficiency and limited performance. In addition, it requires large quantities of water to be used to lubricate and cool the cutter member. Another drawback is that in the event of the cutter member losing teeth inside the borehole, it becomes very difficult, if not impossible, to continue drilling because of the hardness of the teeth of the critter member, which can neither be drilled nor destroyed.